Publications

Tidal currents in an estuary carry all types of dissolved, suspended or floating material. Particle tracking models constitute powerful tools in assessing the transport of this material, through the study of the particles trajectoriesand settling positions. Thus, this work aims at using a Lagrangian particle tracking model driven by hydrodynamic fields to study the impact of morphologic anthropogenic and natural changes in sediments transport at Ria de Aveiro. In fact, as many coastal systems, Ria de Aveiro is in progressive degradation associated to the lack of maintenance and to the strong currents occurring in its channels, which erode theirprotective walls. Hence, the model VELApart, which is driven by the hydrodynamic model ELCIRC (previously calibrated for this lagoon), was applied for two configurations of the Ria de Aveiro: one representing the present situation of the lagoon and another representing a scenario with the enlargement of its flooded area. According tomodel results, morphologic changes influence the sediments pathways and final position, as well as the settling time. Generally for the flooded bathymetry the sediments travel a longer distance and the preferential zones of deposition are inside the flooded area, while for the present configuration sediments settle down in the mainadjacent channels. The settling times also increase with the enlargement of the flooded area.

This study discusses site-specific system optimizationefforts related to the capability of a coastal videostation to monitor intertidal topography. The systemconsists of two video cameras connected to a PC, and isoperating at the meso-tidal, reflective Faro Beach (Algarvecoast, S. Portugal). Measurements from the period February4, 2009 to May 30, 2010 are discussed in this study.Shoreline detection was based on the processing of varianceimages, considering pixel intensity thresholds for featureextraction, provided by a specially trained artificial neuralnetwork (ANN). The obtained shoreline data return ratewas 83%, with an average horizontal cross-shore root meansquare error (RMSE) of 1.06 m. Several empiricalparameterizations and ANN models were tested to estimatethe elevations of shoreline contours, using wave and tidaldata. Using a manually validated shoreline set, the lowestRMSE (0.18 m) for the vertical elevation was obtainedusing an ANN while empirical parameterizations based onthe tidal elevation and wave run-up height resulted in anRMSE of 0.26 m. These errors were reduced to 0.22 m afterapplying 3-D data filtering and interpolation of thetopographic information generated for each tidal cycle.Average beach-face slope tan(

Colwyn Bay beach is undergoing a process of erosion. The present study aims at characterizing the beachdynamics and developing alternative solutions for beach rehabilitation and protection. The method applied tocharacterize the foreshore morphological evolution was the assessment of the shoreline evolution, the analysis ofthe foreshore 3D evolution and the analysis of cross-shore profile evolution. The sedimentologic contents of thebeach were characterized based on the analysis of superficial samples. The hydrodynamic characterization wasbased on the analysis of the wave climate at three inshore points in front of the beach and of the tidal and surgelevels. These data provided the necessary information for the characterization of the longshore transport andevaluation of the beach active zone. The first part of developing alternative solutions was the definition of theoptimum long-term recharged beach profile, which, due to the high tidal range, was calculated based on the2S-EBP method. The beach berm was designed to avoid direct wave action on the seawall existent at the beachbackshore. For that, a morphodynamic model was applied to test the beach retreat under storm events. Finally,alternative long-term solutions based on a nourishment strategy were tested with two shoreline evolution models.Two initial alternative solutions of beach recharge with different grain size sand followed by six alternativesolutions of beach recharge with sand retention structures arrangements were tested. The results, herequalitatively and qu

New experiments under sheet flow conditions were conducted in an oscillating water tunnel to study the effects of flow acceleration on sand transport.The simulated hydrodynamic conditions considered flow patterns that drive cross-shore sediment transport in the nearshore zone: the wave nonlinearitiesassociated with velocity and acceleration skewness and a negative mean current, the undertow. Net transport rates were evaluated from the sedimentbalance equation and show that (1) the acceleration skewness in an oscillatory flow produces a net sediment transport in the direction of the highestacceleration; (2) the net transport in the presence of an opposing current is negative, against the direction of the highest acceleration, and reduces with anincrease in flow acceleration; and (3) velocity skewness increases the values of the net onshore transport rates.

This article defines short-term (tidal cycle) sediment-transport patterns at a backbarrier beach based on detailed fieldstudies. Fieldwork was planned to record nonstorm, spring tide conditions that enable the definition of backgroundsediment dynamics at the study area. The experiment was set at two beach morphologies: beach face and sandbank.Current meters were deployed at both sites. Fluorescent tracer techniques were applied to determine rates and directionof transport. Topographic surveys and sediment sampling were undertaken. During the experiment, limited tracerdisplacement and small morphological changes occurred. The low magnitude changes are representative of predominant,low-energy hydrodynamic conditions. Sediment transport was primarily longshore orientated and dependent on thevelocity of tidal currents. Tidal currents had the potential for sediment transport only during a short period of the tidalcycle and had higher velocities during ebb, which results in a net sediment transport orientated towards the nearby inlet.It is suggested that there is dependence on sediment transport rate at the study site and on the variability of tidalcurrents, which are greatly influenced by the distance to, and conditions of, the nearby Anca

The hydrodynamics of the surf zone in front of collapsing coastal dunes are examined. The data was gatheredduring the HYDRALAB-III funded Transnational Access experiment performed at the CIEM large-scale waveflume. Here, it is presented results of the cross-shore evolution of several flow parameters at four positions. Despikedand band-pass filtered ADV velocity data were used to enable a focus on only the short-wave component.As the waves approach the shore they reduce their (velocity) skewness, but increase their vertical asymmetry.Despite the non-negligible wave reflection, the theoretical wave model of Abreu et al. (2010) was applied tosuccessfully reproduce the measured velocities. Lastly, an estimate of the bed shear stress exerted by the shortwavecomponents is presented.

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Due to the increasing demand of sand for construction and beach nourishment, offshore extraction is being considered as an alternative source. Long term morphological changes caused by such an extraction must bepredicted because they can affect the sediments budget and potentially promote coastal erosion. Numerical models are powerful tools that can help in the evaluation of environmental impacts induced by this activity.The objective of this study is to describe the morphodynamics in the area surrounding a sandpit through the use of the MORSYS2D modelling system. The sandpit under study is located offshore Vale do Lobo, an importantbeach and golf resort located on the Southern Portuguese coast. The numerical solutions of the mean flow and the wave height around the pit were obtained with MORSYS2D between March 28 and April 29, 2008 when two storm events with significant wave height (Hs) greater than 2.5 m occurred.The numerical results are analysed in terms of the sand fluxes and bathymetry changes induced by wind and tidal currents and wave orbital velocities. The results show the strong impact of storm events in the morphologic evolution of the pit and surrounding area. The value for Hs > 2.5m was also confirmed as determinant for thesediment dynamics.

A simple analytical formulation that reproduces a skewed, nonlinear near-bed wave orbital velocity is presented. It contains four free parameters, where two are solely related to the velocity and accelerationskewnesses. The equation is compared with other models and is validated against field and laboratoryexperiments. The results reveal that it can simulate a wide range of nonlinear wave shapes, reproducing satisfactorily the measured nonlinear wave particle velocity. Also, the new expression overcomes somelimitations of the other models. The new formulation is therefore capable of being used in many engineering applications that require the use of representative wave forms.

Three models were applied to analyse the planform of bay-shaped Portuguese beaches. They are based on empirical mathematical functions: the logarithmic spiral bay equation, the hyperbolic tangent bay equation, and the parabolic bay equation. These models were applied to analyse the fitting to the beach planform of 42 beaches on the Portuguese Atlantic coast which was calculated through the validation against the waterline extracted from rectified aerial photographs. The logarithmic spiral model fits well the curved zone of the beaches, in particular small beaches with two headlands. Despite the good fitting of the hyperbolic tangent model for one headland beach, its process of approximation to the solution was less intuitive than the processes of the other two models, therefore its application was more exhaustive. A comparative analysis between the logarithmic spiral model and the hyperbolic tangent model revealed the best fit of the first. The application of the parabolic model allowed to conclude that despite the majority of the beaches analysed being in dynamic equilibrium condition due to the high energy wave regime of the Portuguese Atlantic coast, their planform was very close to the planform in static equilibrium condition due to the high dynamics of the coastal environment

A baía da cidade da Praia, na ilha de Santiago, Cabo Verde, acolhe um dos principais portos comerciais e de cruzeiros de Cabo Verde, tendo também uma relação importante, do ponto de vista ambiental e paisagístico, com a frente ribeirinha da cidade. Procedeu-se a uma análise da evolução morfológica do sistema, com recurso a levantamentos hidrográficos (de 1882 a 2016) e imagens aéreas (de 1968 a 2018), para determinar tendências evolutivas históricas. Realizou-se também a aplicação de um sistema de modelos numéricos, envolvendo a simulação da hidrodinâmica, do transporte sedimentar e da evolução do fundo, para identificar os processos litorais dominantes. Calculou-se uma tendência média de avanço da praia Grande ou da Gamboa de 0,6 a 1,0 m/ano, correspondendo este último valor à média dos últimos 50 anos. As condições de maior hidrodinamismo no interior da baía estão associadas aos períodos de agitação marítima de maior altura. As intervenções mais recentes, nomeadamente na zona portuária, tendem a diminuir esse hidrodinamismo.

This study investigates the roleof infragravity waves (IGW) on the hydrodynamics of a wave-dominated inlet (Albufeira lagoon, Portugal) during storm Leslie (October 2018) through the analysis of field observations. Measured significant IGW heights reached up to 0.9 m in the surf zone, at adjacent ocean beaches, and 0.4 m at the flood-delta. At the flood-delta, IGW were more energetic than wind-generated short-waves by up to a factor of 2. These large IGW are expected to contribute significantly to sediment transport during storm conditions.

Existing knowledge on the evolution of the Tagus estuary inlet morphology derives mostlyfrom analyses of bathymetric surveys and aerial images. The limitations of this approachprevent a detailed understanding of the processes responsible for this evolution, as well as theprediction of the future evolution. A 2DH morhodynamic model was therefore applied to shednew light into the sediment dynamics of this tidal inlet. Description of the method

Due to their exposure to various forcings such as tides and waves, estuary mouths constitute dynamic coastal environments where sediment transport can result in abrupt and significant morphological changes. They concentrate relevant socio-economic and ecological values, which will become even more challenging in the climate change context. Despite their importance worldwide, the dynamics of these environments remains partly understood only and fosters many studies from the scientific community. This work is part of a citizen-science project (named Nouveaux Commanditaires Sciences) which aims at studying the hydro-sedimentary dynamics of the Tagus estuary mouth (bordered by a metropolitan area of 2 million inhabitants), especially during storms, by combining in-situ field observations, remote sensing data and numerical modelling. This research program has been set up following the request for a better understanding of the coastal erosion and marine flooding during storms expressed by severely affected inhabitants from an informal neighbourhood, Segundo Torrão (Southern margin of the inlet). In addition, local populations provide support for instrumental deployments and data acquisitions. In return, new knowledge derived from scientific studies will be used to improve coastal management over these threatened areas. In this presentation, we will present the main actions that are being carried out in the scope of this project.

To increase the response capability to coastal flooding events in an accelerating sea level rise context, the ability to predict floods has to improve and be integrated with other components of risk, such as vulnerability and exposure. The MOSAIC.pt project aims at developing an advanced flood risk management framework for coastal zones, integrating robust predictive tools and multi-source data with the different dimensions of the risk, to adequately contribute to emergency planning and response

Estuarine uses and activities may be negatively affected by climatic variability andclimate change

Os observatórios costeiros podem apoiar a gestão diária e a longo prazo dos sistemascosteiros, permitindo antecipar eventos de contaminação, contribuir para a vigilânciacontínua destas zonas e implementar e adaptar planos de gestão. Ao integrarem previsões,análises de cenários e indicadores, para além de observações históricas e em tempo real, estasferramentas têm aumentado de complexidade ao longo dos anos.

Coastal forecast systems have become reliable tools to support daily coastal management and strategic long-term planning. However, the availability of these systems for most coastal areas remains scarce, in particular for small estuaries and coastal bays, which limits the efficiency of management for these areas from both economic and environmental perspectives. Building a new forecast system or maintaining in operation an existing one requires considerable effort, from both financial and personnel points of view. Accurate forecasts require a team comprising experts in coastal processes and computer science and the availability of robust and large computational resources to maintain the predictions available on a daily basis. Herein, a new concept in forecast tools is presented, building the foundations for forecast systems to be built and made available for all coastal systems worldwide. Denoted OPENCoastS, this freely available web service builds forecasts systems for the coastal area selected by the user and maintains them in operation using the European Open Science Cloud infrastructure. Forecasts are based on the SCHISM community model

The influence of freshwater discharge and sea level rise in the salinity in the upper Tagusestuary is assessed using a numerical model. Results suggest that the river flow is the main driver of the salinity in the upper estuary and that salinity intrusion increases with the duration of the droughts. For the analyzed scenarios, salinity reaches concentrations that are inadequate for irrigation during some periods, which can harm the agricultural activities.

The Tagus estuary (Portugal) supports diverse uses and activities and itsecological value is well recognized. This study aimed to characterize the water quality inthe Tagus estuary during one year, as part of the Tagus estuary observatory. Three fieldcampaigns were performed in 2018 covering distinct seasons (Spring

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The hydrodynamics and sediment dynamics of a low energy estuarine beach was analysed. The beach is subjected to local wind waves generated in an area of restricted fetch, wake waves generated by catamarans and a semi diurnal meso-tidal regime. Only storm events of short duration modify the beach profile, which, once the normal hydrodynamic conditions are restored, naturally recovers its initial shape. The beach is characterised by having a steep upper slope until mean sea level, followed, seaward, by a low gradient terrace, and a bimodal sediment distribution. To investigate the hydro sedimentologic beach behaviour, wind, topo-hydrographic and sedimentologic data were used as input and validation of process based numerical modelling. Wave generation and transformation in an area of restricted fetch, nearshore circulation, sediment transport and morphological evolution were simulated for average annual conditions and storm conditions. The statistical analysis of a six-year wind data series allowed to derive the average wind regime, based on which, the average annual wave regime and the average annual longshore sediment budget, 14.5x103 m3year-1, were calculated. The contribution of the individual components of the representative wave regime, discretised by directional sector and height class of incidence, was evaluated as well as the spatial distribution of the longshore sediment transport in the active part of the beach profile. The characteristics of the wave groups generated by the passage of catamarans at different speeds were estimated and their action on the beach morphology was simulated. Although when the catamarans travel at 20 knots speed the average annual wake wave energy dissipated at the beach is 2.5 times higher than the average annual wind wave energy, the erosion effect on the beach profile is still not relevant for the present traffic. In opposition, short duration storm events generate the formation of an erosion scarp at the upper part of the beach face. The numerical modelling of this phenomenon allowed to acknowledge on the protective effect that the low gradient terrace has on the beach face.

O objectivo do presente trabalho foi o estabelecimento de um modelo matemático do fenómeno da refracção das ondas de gravidade, apoiado num pro¬grama cálculo automático bastante aperfeiçoado e enquadrado por uma técnica de utilização prática que permitisse a resolução rápida dos problemasinerentes ao cálculo de um conjunto de diagramas de refracção, independentemente do número de ondas monocromáticas a analisar.Numa primeira parte, apresentam-se algumas considerações sumárias so¬bre o método de estabelecimento do programa de cálculo e sobre a necessidade de se dispor de um modelo matemático de refracção. A segunda parte é dedicada ao estudo do fenómeno da refracção das on¬das de gravidade e seu tratamento numérico. No Cap.3 indicam-se, de forma Muito sintética, os fundamentos da teoria das ondas de pequena amplitude sendo deduzidas as principais expressões utilizadas no estudo da refracção. É apresentada a teoria da refracção de uma onda sinusoidal, sendo abordado um vasto leque de problemas tais como os aspectos energético e geométrico da refracção, as soluções analíticas para fundos algébricos, as zonas de convergência e cáusticas, a refracção por efeito de correntes, e as aproximações da teoria da refracção. Por último criticam-se os métodos gráficos habituais de cálculo de planos de ondulação. No Cap. 4 são deduzidas as equações de base do tratamento numérico da refracção das ondas sinusoidais como um problema de valores iniciais. No Cap. 5 são apresentadas as dife¬rentes técnicas de cálculo e de interpolação das principais grandezas di¬rectamente ligadas a obtenção de uma ortogonal e dos sucessivos valores da amplitude relativa da onda. São indicados os métodos numéricos de integração das equações diferenciais do raio de onda e do coeficiente de afasta¬mento de ortogonais. E feita referencia a técnicas de alisamento da batimetria. Em todos os casos são apresentados os métodos utilizados no LNEC as¬sim como outros referidos na bibliografia. No Cap. 6 são indicadas, para os vários programas preparados no LNEC, as técnicas de cálculo e de inter¬polação e os métodos numéricos de integração usados. São apresentadas, de uma forma exaustiva, todas as verificações dos programas levadas a cabo após o seu estabelecimento, designadamente a verificação analítica e a comparação dos resultados obtidos com os métodos numéricos e gráficos para fundos ir¬regulares. No âmbito da verificação dos programas é ainda feita referência a resultados obtidos por outros autores e a ensaios em modelo reduzido. Por último tiram-se conclusões sobre a escolha dos programas a lançar em exploração.A terceira e última parte é consagrada à análise do actual programa de cálculo de diagramas de refracção. Assim, no Cap. 7 indicam-se, em li¬nhas muito gerais, o tipo de dados a fornecer, as hipóteses de exploração do programa e o seu modo de funcionamento; é ainda feita uma análise da estrutura do programa, relativamente pormenorizada. 0 Cap. 8 é consagrado à discrição da forma de utilização prática do programa, sendo discutidas as perspectivas de custo da sua utilização cobrindo todas as hipóteses de exploração do programa, ilustrados com os dados e resultados respectivos. No Cap. 9 apresentam-se as conclusões do trabalho e indicam-se as linhas de orientação a seguir no que respeita ao aperfeiçoamento do modelo matemático da refracção e ao estabelecimento de outros modelos matemáticos dependentes ou não daquele.0 texto principal de dissertação encerra-se com 96 referencias bibliográficas, correspondentes aos principais trabalhos consultados pelo autor, na realização do presente estudo; esta bibliografia refere-se a Abril de 1975. Em Anexo no Apêndice I, apresentam-se os elementos referentes aos programas inicialmente estabelecidos no LNEC e cujo aperfeiçoamento posterior conduziu ao programa actualmente em exploração. São indicados, em linhas gerais, as formas possíveis de exploração daqueles programas, o seu modo de funcionamento e os dados a fornecer. É feita uma análise de pormenor da es¬trutura dos programas, sendo descrita a sua forma de utilização prática, e apresentados vários exemplos de aplicação ilustrados com os dados e resul¬tados respectivos. São indicadas algumas verificações efectuadas a estes programas.

0 caminhamento das areias ao longo das costas marítimas é regulado por leis ainda incompletamente apreendidas, mas cujo conhecimento cada vez mais perfeito se torna indispensável no projecto e ensaio em modelo reduzido de grande parte das obras destinadas a solucionar problemas de hidráulica marítima.Começa-se neste trabalho por caracterizar, sob os pontos de vista hidrodinâmico e de movimentação aluvionar, a orla costeira, zona em que o transporte litoral se processa, abordando-se a seguir o aspecto prático mais importante do fenómeno, ou seja, a previsão dos caudais sólidos a partir das características das ondas e do material móvel que forma a praia.Com este último objectivo analisa-se o conjunto dos dados experimentais disponíveis, segundo uma perspectiva baseada na análise dimensional do fenómeno, para a seguir se proceder a um estudo experimental focado sobre a influência do peso específico e do diâmetro do material móvel.Apresentam-se ainda, em anexo, os conceitos básicos respeitantes às correntes longitudinais, fenómeno que teve também de ser objecto de um estudo aprofundado, por estar intimamente relacionado com o transporte sólido litoral.

Este trabalho constitui um estudo em extensão sobre as característi¬cas mais importantes dos perfis transversais das praias e sobre a evolução resultante da actuação da ondulação. Pretendeu-se assim obter um conhecimento geral sobre este assunto, de modo a permitir, por um lado, o melhor planeamento dos trabalhos marítimos e, por outro, uma melhor interpretação dos modelos reduzidos de fundo móvel.Utiliza-se neste trabalho uma nomenclatura original em língua portuguesa, na tentativa de estabelecer uma equivalência com os termos consagrados na literatura siglo-saxónica.Dentro do esquema geral acima enunciado, são estudadas com maior atenção: o mecanismo da movimentação dos materiais nos fundos; a evolução so¬frida pelos perfis em resultado da actuação das ondas e destas em conjugação com as marés; as características da faixa de rebentação das praias; e as variações da granulometria do material móvel.Quanto à movimentação dos materiais em fundos de maior profundidade, apresenta-se uma interpretação sobre as profundidades a que se inicia o transporte dos sedimentos e o sentido desse transporte.Em relação à evolução dos perfis descrevem-se as suas fases mais significativas, quer para o caso de ondas de período e altura crescentes como decrescentes. Introduzem-se os conceitos de perfis de máxima erosão e máximo enchimento.

O presente trabalho baseia-se num estudo experimental sobre o funcionamento hidráulico de esporões marítimos no caso em que estes limitam troços de praia que se comportam, na sua evolução, como unidades fisiográficamente independentes. Pretende-se, com este estudo, contribuir para o conhecimento do mecanismo de evolução de praias em que são construídos campos de esporões, com vista ao projecto de dispositivos funcionais deste tipo de defesa costeira. Acessoriamente, tirando partido dos esporões como meio de medição do caudal sólido litoral, fa¬zem-se algumas considerações sobre as relações existentes entre o transporte litoral e as características da onda actuante.O relatório é constituído pelas seguintes partes : a Introdução, em que se define o objectivo do estudo e as suas características; o capítulo I, em que se apresentam noções gerais sobre esporões; o Capi¬tulo II, em que se dá conhecimento do estudo experimental realizado, definindo o seu planeamento, a tecnologia experimental, as características dos ensaios realizados, a interpretarão dos resultados obtidos e as conclusões; o Capitulo III, que diz respeito a casos reais de emprego de esporões, em que, após umas generalidades, se apresentam as principais características das obras de defesa da Cova do Vapor - Costa da Caparica, do campo de esporões da praia de Espinho e do esporão da praia do Estoril, finalizando com algumas conclusões; o Capítulo IV em que se apresentam considerações sumárias sobre caudal sólido litoral, as quais compreendem algumas generalidades, considerações teóricas, resultados experimen¬tais, observações na natureza e conclusões; finalmente, as Conclusões Finais, onde se agrupam todas as considerações do estudo que se julgam de primordial interesse.

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